Two Olympic spots are at stake in pairs skating this weekend at the U.S. Championships in Boston and two top teams enter into the National Championships having won the event the last time they skated it.

For defending champions Marissa Castelli and Simon Shnapir, it was a year ago that they captured their first-ever national title, while the duo of Caydee Denney and John Coughlin won in 2012, sitting out the competition last year due to injury.

The pairs teams will face a host of competition for berths at the Sochi Olympics during the four-day event at the TD Garden which begins Thursday afternoon and concludes Saturday in the pairs event.

For Denney/Coughlin, the appearance at Nationals marks a continued comeback after a torn labrum in Coughlin’s hip (the same injury that put Evan Lysacek out of the Sochi Games) set the team out following a successful Grand Prix season in 2012.

The Colorado-based team could not defend their national title in Omaha in January and sat out the World Championships in March. But they’ve made marked improvements during the Grand Prix season in 2013, placing fourth at Skate America befor winning bronze at the Grand Prix of France.

“Our technical element score (TES) was at its highest in Paris, [but] we stay humble and continue to work,” Coughlin said on a conference call with reporters. “We’re honest with ourselves and focused on showing that we are an elite team. Our confidence is high after being the best American team on the Grand Prix [this season].”

Castelli/Shnapir would like to prove Coughlin wrong in front of a home crowd in Boston. The team – which has a height diffence of 16 inches (Marissa is 5’0” and Simon is 6’4”) – had a less convincing Grand Prix effort in 2013, missing the podium in both Detroit (sixth) and Tokyo (fourth).

“We’re thrilled that the Championships are here in our backyard,” Shnapir told journalists recently. “Training has been going well and we’ve been working hard going through our programs and sections every single day. We’ve just been drilling everything and feel ready to go.”

Shnapir would be making a return to a different backyard should he and Castelli qualify for the Winter Games: the 26-year-old was born in Moscow before moving to the U.S. with his family when he was just 18 months old, but speaks Russian and would have family members attend in Sochi.

While Denney/Coughlin and Castelli/Shnapir are the clear front-runners to earn the two allotted spots in pairs, there are a host of other teams that will try and throw a wrench in their compatriots’ Olympic plans.

Alexa Scimeca and Chris Knierim, who paired up less than two years ago, were second at Nationals a year ago and had two Grand Prix assignments during the Olympic season, placing fifth at the cup of China and then sixth in Moscow at the Cup of Russia.

Felicia Zhang and Nate Bartholomay, the bronze medalists from the 2013 Nationals, struggled during the Grand Prix season, placing seventh at Skate America and sixth at the Cup of China.

Haven Denney and Brandon Frazier could be the most competitive of the outliers, having placed fifth at both of their Grand Prix assignments. The duo began skating together in 2004 after switching to the ice from roller skating.

Haven is the younger sister to Caydee, meaning a little sibling rivalry could come alive at the TD Garden – or a duo of siblings might be headed to the Olympics not named Shibutani (Maia and Alex, ice dancers).

But the home-ice advantage is something that Castelli hopes to use her own family for in her and Shnapir’s advantage, even if it means a little added pressure during an Olympic season.

“Skating in our hometown is the best advantage that we could have,” Castelli said. “At first I was really nervous, it was really terrifying. But it’s such a blessing to have everyone who supports me come and cheer me on and share this moment with me; it’s going to be so much more motivating. We’re extremely excited.”

The pairs kick off the senior Nationals competition at 4:15 p.m. on Thursday in Boston. NBC will air live coverage of the pairs free skate Saturday afternoon from 3 to 6 p.m. Eastern, as well as host a livestream of the event on NBCOlympics.com.